The Minnesota Vikings' decision to place tailback Adrian Peterson on the physically unable to perform (PUP) list is the last predictable event in his recovery from a serious knee injury. Now it's time to start waiting for the real news to begin.

We knew when Peterson would start running again and when he would begin working on change-of-direction drills. It seemed a certainty that he would open training camp on the PUP list, a move that merely prevents him from getting involved in football drills he couldn't possibly be ready for given the timing of his late-December surgery.

What we don't know is how long it will take Peterson to close the gap between where he is now and the elusive football-ready condition. Players on the PUP can be activated any time between now and the start of Week 1, but if Peterson isn't activated by then, he'll be ineligible for the first six weeks of the season.

There is a general expectation that Peterson will be ready to practice by then, but it's impossible to predict the timing of what happens in between.

"We'll continue to evaluate him daily," coach Leslie Frazier told reporters, "see how he's progressing, and at some point, the doctors and our head trainer Eric Sugarman will come to me and say, 'Hey, we think he's ready to get involved in some team activities.' But at this point, we're going to go through some evaluations, just make a determination as to when is the right time to put him out there with his teammates."

Let the waiting game begin.